Thickened aqueous compositions

ABSTRACT

The invention relates to thickened aqueous compositions which comprise xanthan gum and a water-softening polymer.

This is an application filed under 35 USC 371 of PCT/GB02/03947

The invention relates to thickened aqueous compositions which containxanthan gum and at least one water softening agent.

Water softening products are sold commercially (such as the productCalgon®) and are used to aid detergency and prevent the build up ofscale in the washing machine, such products are described in EP-A1-0 628627 (Benckiser), CH-577 937 (Lonza), WO-A1-95/21908 (Henkel) and EP-A2-0622 449 (Huls).

The use of water-softening polymer polycarboxylates in detergentformulas has provided multiple benefits such as calcium sequestration,crystal growth inhibition to minimize encrustation on fabrics, lime soapdispersancy, and particulate soil dispersion. Sequestration of hardnessions such as calcium and magnesium by the polycarboxylates softens thewater and increases detergency. Also sequestration of hardness ions bythe polycarboxylates prevents the precipitation of salts of anionicsurfactants, which if allowed to occur will lead to reduced detergency.Dispersion of particulate soil such as clay by the polycarboxylatesprevents the redeposition of soils on the fabric. Such polymers are nowfound also in water-softening products.

Conveniently it would be preferred that water-softening products couldbe added to the washing machine as a liquid rather than as a solidproduct. Also it is preferable that the product has a viscosity which isgreater than that of water.

We have found that aqueous compositions of water-softening polymers aredifficult to thicken. In screening for an appropriate gel/thickeningsystem we found that many known systems were not stable or left residueson dark cloths after washing.

WO87/04143 describes a scale removal composition which comprises analpha-hydroxy carboxylic acid and, optionally, a Na silicate which isthickened with xanthan gum.

We have found that xanthan gum can form a thickened stable gel for watersoftening agents which is stable and performs well.

Therefore we present as a feature of the invention an aqueous thickenedcomposition comprising:

-   -   a) a water-softening agent which is a water-soluble polymer;    -   b) water; and    -   c) less than 1.0% wt of a xanthan gum.

Xanthan gum is an acidic, anionic, extracellular heterpolysaccharide,secreted from X. campestris. The polysaccharide is thought to act as aprotective slime, essential for the pathogenecity of the micro-organismtowards its plant host (Rutabaga plant) by blocking fluid flow throughthe xylem.

Xanthan gum is produced by bacterial fermentation and was the firstpolysaccharide produced on large scale using X. campestris. Such atechnique offers the advantage of reproducible physical and chemicalproperties, with a stable cost and supply. Nevertheless, unlike othermicrobial extracellular polysaccharides, the composition of the polymervaries with the Xanthomonas strain and culture conditions and in thepresence or absence of pyruvate and/or acetate substituents.

The polysaccharide forms highly viscous solutions at low polymerconcentrations, which are atypically insensitive to a wide range of saltconcentration, pH and temperature. In addition to this, Xanthansolutions exhibit strong shear thinning behaviour showing non-Newtonianbehaviour, a measurable yield stress from about 1% polymerconcentration, emulsion stabilising and particle suspending abilities,which are all indicative of intermolecular associations.

This natural polysaccharide is widely used in the food industry and to alesser extent the pharmaceutical industry. Most of the commercialXanthan samples contain a variable amount of Na⁺, K⁺, Ca²⁺ salts, andapproximately 30-40% pyruvate content with 60-70% acetate content(although this is subject to variability).

The amount of the water-softening polymer is between 0.1 to 70% wt,ideally, 3 to 50% wt, preferably 15 to 35% wt. Ideally the water-solublepolymer is only partly neutralised.

By the use of the phrase “a water-softening polymer” we preferably meanpolycarboxylate polymers, preferably polyacrylate polymers, based onacrylic acid combined with or without other moieties. These includeacrylic acid combined with; maleic acid (such as Sokalan CP5 and CP7supplied by BASF or Acusol 479N supplied by Rohm & Haas); methacrylicacid (such as Colloid 226/35 supplied by Rhone-Poulenc), phosphonate(such as Casi 773 supplied by Buckman Laboratories), maleic acid andvinyl acetate (such as polymers supplied by Huls), acrylamide,sulfophenol methallyl ether (such as Aquatreat AR 540 supplied by Alco),2-acrylamido-2-methylpropane sulfonic acid (such as Acumer 3100 suppliedby Rohm & Haas or such as K-775 supplied by Goodrich),2-acrylamido-2-methylpropane sulfonic acid and sodium styrene sulfonate(such as K-798 supplied by Goodrich), methyl methacrylate, sodiummethallyl sulfonate and sulfophenol methallyl ether (such as Alcoperse240 supplied by Alco), polymaleates (such as Belclene 200 supplied byFMC), polymethacrylates (such as Tamol 850 from Rohm & Haas),polyaspartates, ethylenediamine disuccinate and organo polyphosphonicacids and their salts such as the sodium salts ofaminotri(methylenephosphonic acid) and ethane 1-hydroxy-1,1-diphosphonicacid.

Preferably the polymer is polyacrylic acid, blended with or without apolymaleic acid polymer, or a polyacrylic/polymaleic acid copolymer(such as those sold by BASF under the Sokalan trademark).

The term “partly neutralised” excludes neutralisation of more than 90%of the free carboxyl groups.

Preferably the average MW (Mw) of the polymer should be greater than1,000, ideally greater than 2,000, based upon the free acid.

Additional water-softening agents may be added to the composition.Preferably the additional water softening agent is a water-soluble watersoftening agent, which is organic or inorganic. Inorganic water-solublewater softening agents that may be present include alkali metal(generally sodium) carbonate; while organic water-soluble watersoftening agent which may be present; monomeric polycarboxylates (suchas citrates, gluconates, oxydisuccinates, glycerol mono-di- andtrisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates,dipicolinates and hydroxyethyliminodiacetates); sequestering agents(such as phosphonates and iminodisuccinates); radical scavengers (suchas BHT); phosphonates (such as diethylenetriaminepenta (methylenephosphonic acid) and its corresponding pentasodium salt, (availableunder the trade names Dequest 2060 and Dequest 2066 Monsanto ChemicalCo.), DTPMP and DTPMA).

The remaining part of the formulating can be water, with up to 95% w/wof the formulation being water, ideally deionised water.

The presence of surfactant is not excluded from this invention. Thisinvention may find use in the preparation of thickened detergent liquidcompositions which contain a water-softening polymer. Preferably thecomposition contains less than 5% wt, ideally less than 1% wt, of asurfactant.

Organic solvents may optionally be added but are not essential in thepresent invention and can be any water-miscible organic solvent.Suitable solvents include C3-C12 alkyl glycol ethers and C1-C4alcohols,such as methanol, ethanol and isopropanol. More preferably, the solventis selected from the group consisting of EGBE, ethylene glycol hexylether (“EGHE”) and mixtures thereof. The solvent is typically present inan amount from about 0.5% to about 4.0%, preferably from about 0.75% toabout 2.5%, and most preferably from about 1.0% to about 2.0% by weightof the composition. EGBE is available from Union Carbide under the tradename Butyl Cellosolve. EGHE is available under the trade name HexylCellosolve from Union Carbide.

The pH, as defined in the present context, is measured in the neatcompositions at 20° C. For optimum stability of these compositions, theneat pH, measured in the above-mentioned conditions, must be in therange of from 3 to 7, ideally from 4 to 6, especially 5.1 to 5.7. The pHof these compositions herein can be regulated by the addition of aBronsted acid or base.

Xanthan gum is a water-soluble polymer. It is soluble in hot and coldwater, as well as being stable in acidic and alkaline conditions (pH1.5-13). The solubility of Xanthan gum allows highly viscous solutionsat low concentrations, i.e., a 1% solution has a viscosity of 800-10000cps (60 rpm/LVF Brookfield viscometer). Preferred viscosities ofsolutions generated are 30 to 3000 cps, preferably 500 to 2000 cps,ideally 1000 to 1500 cps, (measured with a Brookfield LVF, spindle 2, 12rpm @ 20° C.).

Preferred concentrations of xanthan gum are less than 1.00% wt, ideallyless than 0.7% wt, preferably less than 0.5% wt, and especially lessthan 0.4% wt. A preferred source of xanthan gum is Rhodopol T, CAS REGNr. 11138-66-2 (company Rhodia).

A preservative may be added as are commonly found in the field, such as1-(3-Chloroallyl)-3,5,7-triaza-1-azoniaadamantane-chloride (CAS REG Nr.004080-31-3), available as Dowcill 75, at up to 0.1% wt.

An alternative feature of the invention is a method of softening waterin a fabric washing machine which method comprises the addition of acomposition as defined herein above. Preferably the hardness of thewater used in the fabric washing machine is greater than 100 ppm,ideally greater than 150 ppm.

An alternative feature of the invention is the use of xanthan gum inthickening an aqueous composition comprising a water-softeningpolycarboxylate polymer.

Stability

Initial viscosity: 1000-1400 cps (measured with a Brookfield LVF,spindle 2, 12 rpm @ 20° C.)

The system was stable over a period of 3 months over a range ofdifferent conditions.

EXAMPLE

As 100% actives Dehardened Sterilized to 100% Water Sodium Citrate 10-20Water softening  2-10 polymer Xanthan gum 0.1-1.0 Preservative -   0-0.1optional Dye - optional   0-0.1 Perfume - optional   0-0.8

1. A method of softening water in a fabric washing machine which methodcomprises the addition of an aqueous thickened water softeningcomposition which consists essentially of: a) 2-10% wt. of awater-softening agent which is a partly neutralized water-solubleacrylic/maleic copolymer; b) 0-1% wt of a surfactant; c) water; and d)xanthan gum present in an amount of from 0.1% wt. to less than 1.0% wt.to the water of the washing machine, 10-20% wt. of sodium citrate,wherein the aqueous thickened water softening composition comprises 100%wt.
 2. A method according to claim 1 wherein the aqueous thickened watersoftening composition comprises 0.1 to 70% wt of the water-softeningagent.
 3. A method according to claim 2 wherein the aqueous thickenedwater softening composition comprises 3 to 50% wt of the water-softeningagent.
 4. A method according to claim 1 wherein the aqueous thickenedwater softening composition comprises citric acid or a salt thereof. 5.A method according to claim 1 wherein the aqueous thickened watersoftening composition has a pH of from 3 to 7, measured at 20° C.
 6. Amethod according to claim 1 wherein the aqueous thickened watersoftening composition comprises xanthan gum present in an amount of from0.1% wt. and up to but excluding 0.4% wt.
 7. A method according to claim1 wherein the aqueous thickened water softening composition comprises asurfactant.
 8. A method according to claim 1 wherein the aqueousthickened water softening composition comprises an organic solvent.
 9. Amethod according to claim 8 wherein the aqueous thickened watersoftening composition comprises an organic solvent selected from C3-C12all glycol ethers, and C1-C4 alcohols.
 10. A method according to claim 8wherein the aqueous thickened waters softening composition comprises anorganic solvent selected from the group consisting of: ethylene glycolbutyl ether, ethylene glycol hexyl ether, and mixtures thereof.
 11. Amethod according to claim 1 wherein the aqueous thickened watersoftening, composition comprises a phosphonate.
 12. A thickened liquidwater softening composition comprising a) 2-10% wt. of a water-softeningagent which is a water-soluble polymer; b) less than 1% wt of asurfactant; c) water; and d) 0.1% wt. to less than 1.0% wt of a xanthangum, 10-20% wt. of sodium citrate, wherein the thickened aqueouscomposition comprises 100% wt.
 13. A thickened liquid water softeningcomposition according to claim 10 comprising 0.1 to 70% wt of awater-softening polyacrylate polymer.
 14. A thickened liquid watersoftening composition according to claim 11 comprising 3 to 50% wt of awater-softening polycarboxylate polymer.
 15. A thickened liquid watersoftening composition according to claim 10, wherein the water-softeningpolycarboxylate polymer is a polymer based on acrylic acid combined withor without other moieties.
 16. A thickened liquid water softeningcomposition according to claim 13 wherein the water-softeningpolycarboxylate polymer is an acrylic/maleic copolymer.
 17. A thickenedliquid water softening composition according to claim 10 whichadditionally comprises citric acid or a salt thereof.
 18. A thickenedliquid water softening composition according to claim 10 whichadditionally comprises a phosphonate.
 19. A thickened liquid watersoftening composition according to claim 10 wherein the pH of thecomposition is from 3 to 7, measured at 20° C.
 20. A thickened liquidwater softening composition according to claim 10 comprising from 0.1%wt. to less than 0.4% wt of a xanthan gum.
 21. A method of softeningwater in a fabric washing machine which method comprises the addition ofa thickened liquid water softening composition according to claim 10.22. A thickened liquid water softening composition according to claim 10consisting essentially of: a) 2-10% wt. water-softening agent which is awater-soluble polymer; b) less than 1% wt of a surfactant; c) water; andd) 0.1% wt. to 1.0% wt of a xanthan gum.